从一对多关系中获得一对一的结果
答
如何:
select *
from order
where order_number in
(select order_number
from order_details
group by order_number
having count(*) = 1)
+0
谢谢pm_2这个很好用 – Ahmed 2010-06-30 09:11:43
答
SELECT O1.order_number
FROM Orders AS O1
WHERE 1 = (
SELECT COUNT(*)
FROM OrderDetails AS D1
WHERE O1.order_number = D1.order_number
);
你可以发布你的数据和你想要的结果的例子吗?还有表结构呢?人们无法猜测你的具体情况是什么。如果您添加了您正在使用的数据库系统,它也将有所帮助,因为语法可能略有不同,具体取决于它是哪一个。 – Oded 2010-06-30 07:18:00
我使用ms sql,我的表格结构非常复杂,我找到了pm_2很好的答案 – Ahmed 2010-06-30 09:12:52